The roots of the eqn x^2-8x+h
are (alpha) and (alpha+3k)
Express h in terms of k
I will guess that the author of the assignment forgot the "equals zero" part of the "equation". (Without the "equals" sign, it's not an "equation"; without the assumption that the other side was "zero", there's no way to find the roots.)
In case you haven't learned about the formulas relating the roots of a quadratic function to the coefficients, you can instead use the relationship between roots and factors to find the factorization:
. . . . .
In your case, the zeroes are:
. . . . .
Then the factors must have been:
. . . . .
Multiplying, we get:
. . . . .
Comparing coefficients, we see that:
. . . . .
Then:
. . . . .
Comparing coefficients again, we see that:
. . . . .
Substituting from above, we get:
. . . . .
. . . . .
...which simplifies to give a result equivalent to the previous reply.